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Subject: Re: [PATCH 1/2] of_pci_irq: add a check to fallback to standard
 device tree parsing
From:   Ryder Lee <ryder.lee@mediatek.com>
To:     Rob Herring <robh+dt@kernel.org>
CC:     "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        <linux-mediatek@lists.infradead.org>, <linux-pci@vger.kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        "Frank Rowand" <frowand.list@gmail.com>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>
Date:   Fri, 2 Feb 2018 17:32:50 +0800
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References: <31c765c53e85e41bfc001d110d69e46c9967f4e7.1516961656.git.ryder.lee@mediatek.com>
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On Wed, 2018-01-31 at 10:02 -0600, Rob Herring wrote:
> On Wed, Jan 31, 2018 at 1:41 AM, Ryder Lee <ryder.lee@mediatek.com> wrote:
> > A root complex usually consist of a host bridge and multiple P2P bridges,
> > and someone may express that in the form of a root node with many subnodes
> > and list all four interrupts for each slot (child node) in the root node
> > like this:
> >
> >         pcie-controller {
> >                 ...
> >                 interrupt-map-mask = <0xf800 0 0 7>;
> >                 interrupt-map = <0x0000 0 0 {INTx} &{interrupt parent} ...>
> >                                  0x0800 0 0 {INTx} &{interrupt parent} ...>;
> >
> >                 pcie@0,0 {
> >                         reg = <0x0000 0 0 0 0>;
> >                         ...
> >                 };
> >
> >                 pcie@1,0 {
> >                         reg = <0x0800 0 0 0 0>;
> >                         ...
> >                 };
> >         };
> >
> > As shown above, we'd like to propagate IRQs from a root port to the devices
> > in the hierarchy below it in this way.  However, it seems that the current
> > parser couldn't handle such cases and will get something unexpected below:
> >
> >         pcieport 0000:00:01.0: assign IRQ: got 213
> >         igb 0000:01:00.0: assign IRQ: got 212
> >
> > There is a device which is connected to 2nd slot, but the port doesn't share
> > the same IRQ with its downstream devices.  The problem here is that, if the
> > loop found a P2P bridge, it wouldn't check whether the reg property exists
> > in ppnode or not but just pass the subordinate devfn to of_irq_parse_raw(),
> > thus the subsequent flow couldn't correctly resolve them.
> >
> > Fix this by adding a check to fallback to standard device tree parsing.
> >
> > Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
> > ---
> > Please refer to the previous discussion thread: https://patchwork.ozlabs.org/patch/829108/
> > ---
> >  drivers/of/of_pci_irq.c | 14 ++++++++++++--
> >  1 file changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/of/of_pci_irq.c b/drivers/of/of_pci_irq.c
> > index 3a05568..e445866 100644
> > --- a/drivers/of/of_pci_irq.c
> > +++ b/drivers/of/of_pci_irq.c
> > @@ -86,8 +86,18 @@ int of_irq_parse_pci(const struct pci_dev *pdev, struct of_phandle_args *out_irq
> >         out_irq->np = ppnode;
> >         out_irq->args_count = 1;
> >         out_irq->args[0] = pin;
> > -       laddr[0] = cpu_to_be32((pdev->bus->number << 16) | (pdev->devfn << 8));
> > -       laddr[1] = laddr[2] = cpu_to_be32(0);
> > +
> > +       if (!dn && ppnode) {
> 
> I would think whether you have a child device in DT or not is
> irrelevant. If it's the bridge address you need to look at for
> resolving interrupts, that would be true regardless.
> 
> > +               const __be32 *addr;
> > +
> > +               addr = of_get_property(ppnode, "reg", NULL);
> > +               if (addr)
> > +                       memcpy(laddr, addr, 3);
> 
> Can't you just adjust pdev to be ppdev in this case and then use the
> existing code to set laddr?

Okay, I will try it out and and see if the code gets better or worse.
 
> Please copy the powerpc list on this. I worry that touching this
> function will break something.
> BTW, this code is moving to drivers/pci/ in 4.16.

Sure. I will loop more people in next version.

Thanks

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